EMC Manual ServodynT, D
Switch cabinet structure
38
1070 066 074-101
3.5
Earthing
The following are taken into account as a part of the earthing plan:
-
protective earth
as protection against dangerous shock currents
-
functional earthing
as protection for sensitive electrical equipment
! DANGER !
Dangerous shock currents due to insufficient PE conductor connections.
Do not allow PE conductor connections to be impaired by mechanical, chemical or electrochemi
cal influences. The connection should be permanently fixed.
The equipotential bonding should be configured in mesh or surface form
as it then has a smaller impedance than a pointtopoint equipotential
bonding. Loops in the earthing system have a reducing effect with mesh
type equipotential bonding, as the magnetic field of the induced currents
is inverse to the exciting magnetic field.
Surfacetype equipotential bonding is:
d
the mounting plate in the switch cabinet
d
the surface of the metallic machine frames which the motors are
attached to.
To prevent circulating currents at system frequency, all system parts
should, if possible, be supplied from one connecting point of the supply
system.
!
3.1
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